US4915080A - Electronic air-fuel ratio control apparatus in internal combustion engine - Google Patents

Electronic air-fuel ratio control apparatus in internal combustion engine Download PDF

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Publication number
US4915080A
US4915080A US07/246,746 US24674688A US4915080A US 4915080 A US4915080 A US 4915080A US 24674688 A US24674688 A US 24674688A US 4915080 A US4915080 A US 4915080A
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Prior art keywords
air
fuel ratio
fuel
engine
nitrogen oxides
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US07/246,746
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English (en)
Inventor
Shinpei Nakaniwa
Akira Uchikawa
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Hitachi Unisia Automotive Ltd
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Japan Electronic Control Systems Co Ltd
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Priority claimed from JP23630087A external-priority patent/JPS6480749A/ja
Priority claimed from JP62238957A external-priority patent/JPH0786332B2/ja
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Assigned to JAPAN ELECTRONIC CONTROL SYSTEMS CO., LTD. reassignment JAPAN ELECTRONIC CONTROL SYSTEMS CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: NAKANIWA, SHINPEI, UCHIKAWA, AKIRA
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1473—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the regulation method
    • F02D41/1475—Regulating the air fuel ratio at a value other than stoichiometry
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/146—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an NOx content or concentration
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
    • F02D41/1456—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio with sensor output signal being linear or quasi-linear with the concentration of oxygen

Definitions

  • the present invention relates to an air-fuel ratio control apparatus in which a fuel injection valve arranged in an intake passage of an internal combustion engine is pulse-controlled in an on-off manner and an optimum air-fuel ratio in an air-fuel mixture sucked in the engine is obtained by electronic feedback control correction. More particularly, the present invention relates to an air-fuel ratio control apparatus in which the amounts discharged of nitrogen oxides (NO x ) and unburnt components (CO, HC and the like) are reduced.
  • NO x nitrogen oxides
  • CO, HC and the like unburnt components
  • This basic fuel injection quantity is corrected according to the engine temperature and the like and feedback correction is performed based on a signal from an oxygen sensor for detecting the air-fuel ratio of the air-fuel mixture by detecting the oxygen concentration in the exhaust gas, and correction based on a battery voltage or the like is carried out and a fuel injection quantity Ti is finally set.
  • the air-fuel ratio feedback correction based on the signal from the oxygen sensor is performed so that the airfuel ratio is controlled to a value close to the target airfuel ratio (theoretical air-fuel ratio).
  • the reason is that the conversion efficiency (purging efficiency) of a ternary catalyst disposed in the exhaust system to oxidize CO and HC (hydrocarbon) in the exhaust gas and reduce N O for purging the exhaust gas is set so that a highest effect is attained for an exhaust gas discharged when combustion is performed at the theoretical air-fuel ratio.
  • This system comprises a ceramic tube having an oxygen ion-conducting property and a platinum catalyst layer for promoting the oxidation reaction of CO and HC in the exhaust gas, which is laminated on the outer surface of the ceramic tube.
  • O 2 left at a low concentration in the vicinity of the platinum catalyst layer on combustion of an air-fuel mixture richer than the theoretical air-fuel ratio is reacted in a good condition with CO and HC to lower the O 2 concentration substantially to zero and increase the difference between this reduced O 2 concentration and the O 2 concentration in the open air brought into contact with the inner surface of the ceramic tube, whereby a large electromotive force is produced between the inner and outer surfaces of the ceramic tube.
  • the generated electromotive force (output voltage) of the oxygen sensor has such a characteristic that the electromotive force abruptly changes in the vicinity of the theoretical air-fuel ratio, as pointed out above.
  • This output voltage V 02 is used as the reference voltage (slice level SL) to judge whether the air-fuel ratio of the air-fuel mixture is richer or leaner than the theoretical air-fuel ratio.
  • the air-fuel ratio feedback correction coefficient LAMBDA to be multiplied to the above-mentioned basic fuel supply quantity Ti is gradually increased (decreased) by predetermined integration constant, whereby the air-fuel ratio is controlled to a value close to the theoretical air-fuel ratio.
  • the above-mentioned ternary catalyst can effectively reduce any of the amounts of CO, HC and NO x at the control of the air-fuel ratio to the theoretical air-fuel ratio.
  • NO x since the change of the conversion in the vicinity of the theoretical air-fuel ratio is large, in view of the dispersion of parts or the like, it is difficult to obtain a high conversion stably.
  • the oxygen component in NO x should be detected as a part of the oxygen concentration in the exhaust gas, this oxygen cannot be grasped by the oxygen sensor, reversion of the electromotive force tends to occur at the air-fuel ratio leaner by the oxygen component in NO x than the theoretical air-fuel ratio and the air-fuel ratio is controlled to a lean value, whereby reduction of the conversion of NO x in the ternary catalyst is promoted.
  • the electromotive force of the oxygen sensor is reversed at the true air-fuel ratio.
  • This true air-fuel ratio is a value shifted to a rich side by the oxygen component in NO x from the theoretical air-fuel ratio at which the electromotive force is reversed when the oxygen sensor having no capacity of reducing NO x . Accordingly, if this oxygen sensor is used, the air-fuel ratio is shifted to a rich side and controlled to a value close to the true theoretical air-fuel ratio.
  • the air-fuel ratio is controlled to a substantially constant level irrespectively of the NO x concentration, the conversions of CO, HC and NO x are sufficiently increased in the ternary catalyst, and the amounts discharged of CO and HC can be most effectively reduced and the NO x content can be effectively lowered, with the result that omission of the EGR apparatus becomes possible.
  • the oxygen sensor provided with the NO x -reducing catalyst when the amount of CO as the base is smallest, the reduction reaction of 2CO +2NO ⁇ N 2 +2CO 2 is not caused and shifting of the output-reversing region in the vicinity of the theoretical air-fuel ratio becomes impossible. Accordingly, the output-reversing region cannot be brought to the point of improving the conversion of NO x (true theoretical air-fuel ratio) of the ternary catalyst at the time when the amount of NO x is largest, and a function of stably reducing NO x can hardly be obtained.
  • the air-fuel ratio In the region where the NO x concentration is low, if the air-fuel ratio is controlled to a value slightly leaner than the theoretical air-fuel ratio, the unburnt components CO and HC are more reduced, and hence, this control is preferred. However, even if the air-fuel ratio is controlled to a rich side, the amount discharged of NO x is decreased and the amounts discharged of CO and HC are increased, but since the efficiency of conversion of CO and HC can be increased more easily than the efficiency of conversion of NO x in the ternary catalyst, even in the region of a low NO x concentration, as in the region of a high NO x concentration, the control can be facilitated by setting the theoretical air-fuel ratio at a richer level.
  • the present invention has been completed so as to solve the foregoing problems. It is therefore a primary object of the present invention to provide an air-fuel control apparatus in which at least in the driving state where the amount formed of NO x is large, the target air-fuel ratio controlled by an oxygen sensor provided with an NO x -reducing catalyst is shifted to a value richer than the theoretical air-fuel ratio, whereby the foregoing problems are solved.
  • a secondary object of the present invention is to change the target air-fuel ratio controlled by an oxygen sensor provided with an NO x -reducing catalyst according to the amount formed of NO x .
  • Another object of the present invention is to set the target air-fuel ratio controlled by a oxygen sensor provided with an NO x -reducing catalyst at a level richer than the theoretical air-fuel ratio in the driving state where the amount formed of NO x is large and set the target air-fuel ratio at a leaner level in the driving state where the amount formed of NO x is small.
  • the change and control of the target air-fuel ratio can be accomplished by changing and setting the reference value or slice level SL, with which the output value of the oxygen sensor provided with the reducing catalyst is compared.
  • the change and control of the target air-fuel ratio can be accomplished by changing and setting the feedback control constant in the feedback control means for eliminating the deviation of the actually detected air-fuel ratio from the target air-fuel ratio.
  • an air-fuel ratio control apparatus in an internal combustion engine, which comprises, as shown in FIG. 1, an oxygen sensor provided with a ternary catalyst and arranged in an exhaust passage to detect the oxygen concentration in an exhaust gas, corresponding to the air-fuel ratio in an air-fuel mixture supplied to the engine, said oxygen sensor comprising a catalyst for reducing NO x (nitrogen oxides) and having such a characteristic that the output value is reversed in the vicinity of the target air-fuel ratio, and air-fuel ratio feedback control means for comparing the output value of the oxygen sensor with a reference value corresponding to the target air-fuel ratio and performing the control of increasing or decreasing the fuel injection quantity to control the air-fuel ratio to a level close to the target air-fuel ratio, wherein target air-fuel ratio-setting means is disposed to set the target air-fuel ratio and change the target air-fuel ratio to a level richer than the theoretical air-fuel ratio at least in the state where the NO x concentration in the exhaust gas is high.
  • the air-fuel ratio is set at a level richer than the theoretical air-fuel ratio at least in the state where the NO x concentration in the exhaust gas is high, the NO x conversion in the ternary catalyst can be increased to a level close to the upper limit.
  • the target air-fuel ratio can be set so that it is changed according to the amount generated of NO x , or when the amount generated of NO x is large, the target air-fuel ratio can be set at a level richer than the theoretical air-fuel ratio and when the amount generated of NO x is small, the target air-fuel ratio can be set at a leaner level.
  • the reason is that in the case where the amount generated of NO x is small, if the air-fuel ratio is shifted to a lean side, the amounts of CO and HC can be reduced.
  • the reference value, with which the output value of oxygen sensor provided with the reducing catalyst is compared may be changed, or the feedback control constant in the feedback control means may be changed so as to eliminate the deviation of the actually detected air-fuel ratio from the target air-fuel ratio.
  • FIG. 1 is a block diagram illustrating the structure of the present invention.
  • FIG. 2 is a sectional view illustrating the main part of an oxygen sensor used in one embodiment of the present invention.
  • FIG. 3 is a diagram illustrating the system of the embodiment shown in FIG. 2.
  • FIG. 4 is a flow chart showing a fuel injection quantity control routine in the embodiment shown in FIG. 2.
  • FIG. 5 is a flow chart showing a feedback correction coefficient-setting routine in the embodiment shown in FIG. 2.
  • FIG. 6 is a diagram illustrating the characteristics of the oxygen sensor in the embodiment shown in FIG. 2.
  • FIG. 7 is a diagram illustrating the characteristics of a ternary catalyst used in the embodiment shown in FIG. 2.
  • FIG. 8 is a diagram illustrating the concentration characteristics of various exhaust gas components.
  • FIG. 9 is a flow chart showing a feedback correction coefficient-setting routine in another embodiment of the present invention.
  • FIG. 10 is a time chart illustrating the changes of the feedback correction coefficient and the output voltage of the oxygen sensor at the time of the control in the embodiment shown in FIG. 9.
  • FIG. 2 illustrates the structure of a sensor portion of an oxygen sensor used in one embodiment of the present invention.
  • inner and outer electrodes 2 and 3 composed of platinum are formed on parts of the inner and outer surfaces of a ceramic tube 1, as the substrate, which is composed mainly of zirconium oxide (ZrO 2 ) which is a solid electrolyte having an oxygen ion-conducting property and has a closed top end portion. Furthermore, a platinum catalyst layer 4 is formed on the surface of the ceramic tube 1 by vacuum deposition of platinum. The platinum catalyst layer 4 is an oxidation catalyst layer for promoting the oxidation reaction of CO and HC in the exhaust gas.
  • ZrO 2 zirconium oxide
  • An NO x -reducing catalyst layer 5 (having, for example, a thickness of 0.1 to 5 ⁇ m) is formed on the outer surface of the platinum catalyst layer 4 by incorporating particles of a catalyst for promoting the reduction reaction of nitrogen oxides NO x , such as rhodium Rh or ruthenium Ru (in an amount of, for example, 1 to 10%), into a carrier such as titanium oxide TiO 2 or lanthanum oxide La 2 O 3 .
  • a metal oxide such as magnesium spinel is flame-sprayed on the outer surface of the NO x -reducing catalyst layer 5 to form a protecting layer 6 for protecting the platinum catalyst layer 4 and the NO x -reducing catalyst layer 5.
  • Rhodium Rh and ruthenium Ru are publicly known as catalysts for reducing nitrogen oxides NO x , and it has been experimentally confirmed that if titanium oxide TiO 2 or lanthanum oxide La 2 O 3 is used as the carrier for this catalyst, the reduction reaction of NO x can be performed much more efficiently than in the case where ⁇ -alumina or the like is used as the carrier.
  • the protecting layer 6 is formed on the outer surface of the reducing catalyst layer 5, but there may be adopted a modification in which the protecting layer 6 is formed between the platinum catalyst layer 4 and the NO x -reducing catalyst layer 5.
  • the amounts of the unburnt components CO and HC to be reacted with 0 2 arriving at the platinum catalyst layer 4 located on the inner side of the NO x -reducing layer 5 are reduced by the above reactions in the NO x -reducing catalyst layer 5, and the O 2 concentration is accordingly increased.
  • the concentration difference between the O 2 concentration on the inner side of the ceramic tube 1 falling in contact with the open air and the O 2 concentration on the exhaust gas side is reduced, the therefore, the electromotive force of the oxygen sensor is reversed below the reference value (slice level) and reduced on the side richer than in the conventional oxygen sensor in which the NO x components in the exhaust gas are not reduced, with the result that lean detection can be performed.
  • the air-fuel ratio is controlled to a rich level closer to the true theoretical air-fuel ratio, obtained by detecting the oxygen concentration while taking the oxygen component of NO x into account.
  • the NO x -reducing catalyst layer 5 has also a function of promoting the reaction of the unburnt components CO and HC with O 2 . However, since this function is substituted for the function of the platinum catalyst layer 4, the O 2 concentration on the exhaust gas side is not reduced.
  • an air flow meter 13 for detecting the sucked air flow quantity Q and a throttle valve 14 for controlling the sucked air flow quantity Q co-operatively with an accelerator pedal are arranged on an intake passage 12 of an engine 11, and electromagnetic fuel injection valves 15 for respective cylinders are arranged in a manifold portion located downstream.
  • Each fuel injection valve 15 is opened and driven by an injection pulse signal from a control unit 16 having a microcomputer built therein to inject and supply a fuel fed under a pressure from a fuel pump not shown in the drawings and maintained under a predetermined pressure controlled by a pressure regulator.
  • a water temperature sensor 17 for detecting the cooling water temperature Tw in a cooling jacket of the engine 11 is arranged, and an oxygen sensor 19 (see FIG.
  • crank angle sensor 21 is built in a distributor not shown in the drawings, and the revolution number of the engine is detected by counting for a predetermined time crank unit angle signals put out from the crank angle sensor 21 synchronously with the revolution of the engine or by measuring the frequency of crank reference angle signals.
  • the routine of the control of the air-fuel ratio by the control unit 16 will now be described with reference to the flow chart shown in FIG. 4, which illustrates the fuel injection quantity-computing routine.
  • This routine is carried out at a predetermined frequency (for example, 10 ms).
  • step (indicated by "S" in the drawings) the basic fuel injection quantity Tp corresponding to the flow quantity Q of sucked air per unit revolution is computed from the sucked air flow quantity Q detected by the air flow meter 13 and the engine revolution number N calculated from the signal from the crank angle sensor 21 according to the following formula:
  • Tp K ⁇ Q/N (K is a constant)
  • various correction coefficients COEF are set based on the cooling water temperature Tw detected by the water temperature sensor 17 and other factors.
  • step 3 the feedback correction coefficient LAMBDA set based on the signal from the oxygen sensor 19 by the feedback correction coefficient-setting routine, described hereinafter, is read in.
  • the voltage correction portion Ts is set based on the voltage value of the battery. This is to correct the change of the injection quantity in the fuel injection valve 15 by the change of the battery voltage.
  • the final fuel injection quantity Ti is computed according to the following formula:
  • the computed fuel injection quantity Ti is set at the output register.
  • the portion including steps 5 and 6 shows a fuel injection quantity computing means.
  • the engine driving state detecting means includes the air flow meter 13, the crank angle sensor 21, the water temperature sensor 17 and others.
  • a driving pulse signal having a pulse width of the computed fuel injection quantity Ti is given to the fuel injection valve 15 at the predetermined timing synchronous with the revolution of the engine to effect injection of the fuel.
  • the air-fuel ratio feedback control correction coefficient LAMBDA-setting routine having the feedback control constant-setting function according to the present invention will now be described with reference to FIG. 5.
  • This routine is carried out synchronously with the revolution of the engine and shows an air-fuel ratio feedback control means by incorporated with the routine shown in FIG. 4.
  • the signal voltage V 02 from the oxygen sensor 19 is read in.
  • the first reference value SL O (slice level), with which the signal voltage V 02 is to be compared, is retrieved from the map stored in ROM based on newest data of the present engine revolution number N and the basic fuel injection quantity Tp.
  • This step 12 corresponds to a first target air-fuel ratio setting means according to the present invention.
  • the driving region is finely divided by N and Tp, and in the region where the combustion temperature is high and the NO x discharge concentration is increased (experimentally determined and retrieving these regions corresponds to a nitrogen oxides concentration detecting means according to the present invention), the second reference value SL H of a relatively high voltage corresponding to the air-fuel ratio richer than the true theoretical air-fuel ratio is set (this function corresponds to a second target air-fuel setting means according to the present invention), and in the other region where the NO x concentration is relatively low, the first reference value SL O of a relatively low voltage corresponding to the true theoretical air-fuel ratio is set.
  • other setting can be optionally set according to the NO x concentration.
  • the map of the reference value SL stored in ROM and the function of changing over and setting the reference value in the map correspond to the first and second target air-fuel ratios-setting means.
  • step 13 the routine goes into step 13, and the signal voltage V 02 read in at step 11 is compared with the reference value SL (SL O or SL H ) retrieved at step 12.
  • the routine goes into step 14, and it is judged whether or not the lean air-fuel ratio has been reversed to the rich air-fuel ratio.
  • the feedback correction coefficient LAMBDA is decreased by a predetermined proportion constant P.
  • the routine goes into step 16 and the precedent value of the feedback correction coefficient LAMBDA is decreased by a predetermined integration constant I.
  • step 13 When it is judged at step 13 that the air-fuel ratio is lean (V 02 ⁇ SL), the routine goes into step 17 and it is similarly judged whether or not the rich air-fuel ratio has been reversed to the lean air-fuel ratio.
  • the step 13 corresponds to an air-fuel ratio judging means according to the present invention.
  • the routine goes into step 18 and the feedback correction coefficient LAMBDA is increased by a predetermined proportion P.
  • the routine goes into step 19 and the precedent value is increased by a predetermined integration constant I.
  • the feedback correction coefficient LAMBDA is increased or decreased at a certain gradient.
  • the relation of I ⁇ P is established. (In general, the proportion constant P is included in the integration constant I.)
  • the second reference value SL H is elevated, whereby the point of the reversion between the rich and lean air-fuel ratios is shifted to the rich side. Since increase-decrease of the feedback correction coefficient LAMBDA is changed over with this reversion point being as the boundary, and therefore, the central value of the control of the air-fuel ratio, that is, the target air-fuel ratio, is shifted to the rich side.
  • the air-fuel ratio is controlled to a level richer than the true theoretical air-fuel ratio, as shown in FIG. 6, the NO x conversion is stabilized at a sufficiently high level, as is apparent from the characteristics shown in FIG. 7, and even if temporary reduction of the air-fuel ratio to a lean side is caused by the dispersion of parts or deterioration or based on the fuel supply delay at the initial stage of the transitional driving state of the engine, excessive reduction of the air-fuel ratio to a lean side is not caused and a good NO x -reducing function can be stably maintained.
  • the NO x conversion is sufficiently improved.
  • the conversion of CO and HC is not so largely changed according to the hange of the air-fuel ratio as the NO x concentration, and therefore, reduction of the conversion is only very small.
  • the rich control of the air-fuel ratio is not always performed but is performed only in the region where the NO x concentration is high, and the CO and HC concentrations are low in the region where the NO x concentration is high, as shown in FIG. 8. Accordingly, increase of the amounts discharged of CO and HC are sufficiently controlled.
  • the injected fuel flows along the inner wall of the intake passage in the state adhering thereto, and hence, the amount of the fuel is not effectively increased for acceleration, with the result that the air-fuel ratio is temporarily made leaner than the target air-fuel ratio and the NO x concentration tends to increase.
  • the second target air-fuel ratio is controlled to a level richer than the theoretical air-fuel ratio, even if the above-mentioned reduction of the air-fuel ratio to a lean side is encountered, substantial reduction of the actual air-fuel ratio below the theoretical air-fuel ratio can be prevented.
  • the reference value to the output voltage of the oxygen sensor 19 is set at a low level, and therefore, the air-fuel ratio corresponding to the reference value SL O is shifted to a level leaner than the air-fuel ratio in the region where the NO x concentration is high. Accordingly, the air-fuel ratio is controlled to a value close to the true theoretical air-fuel ratio.
  • the conversions of NO x , CO and HC in the ternary catalyst are sufficiently high, the effect of reducing NO x , CO and HC is enhanced. Taking into consideration of the temporal lean phenomena of the air-fuel ratio is not needed since the fuel delay region which possibly occurs in the case of the engine transient state is not included in the low NO x concentration.
  • the concentrations of CO, HC and NO x can be reduced with a good balance and the overall exhaust gas emission performance can be greatly improved.
  • this surging can be controlled by controlling the ignition timing to an advance side, and also in this case, since the increased amount of NO x can be reduced by performing the control according to the present invention, surging can be effectively controlled.
  • the first feedback control constant is retrieved from the map stored in ROM based on newest data of the present engine revolution number N and basic fuel injection quantity Tp.
  • the feedback control constant comprises the second proportion constant Pr to be added for correction of increase of the fuel supply quantity just after the rich air-fuel ratio has been reversed to the lean air-fuel ratio and the second integration constant Ir to be added for correction of increase of the fuel supply quantity at the time other than the point just after the above-mentioned reversion of the air-fuel ratio.
  • the feedback control constant comprises the first proportion constant Pl to be subtracted for correction of decrease of the fuel supply quantity just after the lean air-fuel ratio has been reversed to the rich air-fuel ratio and the first integration constant Il to be subtracted for correction of decrease of the fuel supply quantity at the time other than the point just after the above-mentioned reversion of the air-fuel ratio.
  • the feedback control constant includes two kinds of constants, each of which has the integration constant and the proportion constant.
  • step 12 In the region where the NO x concentration in the exhaust gas is high, for example, in the hatched region in the graph shown at step 12 which corresponds to the nitrogen oxygen concentration detecting means, the second proportion constant Pr and integration constant Ir for correction of increase of the fuel supply quantity are set at values larger than the first proportion constant Pl and integration constant Il for correction of decrease of the fuel supply quantity, respectively. In the other region where the NO x concentration is low, the second proportion constant Pr and integration constant Ir are set at values almost equal to the first proportion constant Pl and integration Il, respectively.
  • the portion of step 12A corresponds to the feedback control constant-setting means which includes the first and second target air-fuel ratio setting means or the first and second feedback control constant-setting means.
  • the second values of Pr and Ir may be optionally set according to the NO x concentration.
  • step 13A the routine goes into step 13A, and the signal voltage V 02 read in at step 11 is compared with the fixed reference value SL H (theoretical air-fuel ratio).
  • the routine goes into step 14A and it is judged whether or not the lean air-fuel ratio has been reversed to the rich air-fuel ratio, which corresponds to the air-fuel ratio judging means.
  • the feedback correction coefficient LAMBDA is decreased by the proportion constant Pl retrieved at step 12.
  • the routine goes into step 16A, and the precedent value of the feedback correction coefficient LAMBDA is decreased by the retrieved integration constant Il.
  • step 13 When it is judged at step 13 that the air-fuel ratio is lean (V 02 >SL), the routine goes into step 17A and it is judged whether or not the rich air-fuel ratio has been reversed to the lean air-fuel ratio.
  • the routine goes into step 18A and the feedback correction coefficient LAMBDA is increased by the retrieved proportion Pr.
  • the routine goes into step 19A and the precedent value of the feedback correction coefficient LAMBDA is increased by the integration constant Ir.
  • the feedback correction coefficient LAMBDA is thus increased or decreased at a certain gradient. Incidentally, the relation of Ir, Il, Pr, Pl is established.
  • the feedback correction coefficient LAMBDA is changed as shown in FIG. 10, and the proportion of the time during which the air-fuel ratio is at a rich level increases in case of Pr ⁇ Pl and Ir ⁇ Il. Namely, the control central value of the air-fuel ratio (target air-fuel ratio) is shifted to the rich side.
  • the amounts discharged of CO, HC and NO x can be reduced as much as possible, and the overall exhaust gas emission characteristics can be improved throughout the entire driving region.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
US07/246,746 1987-09-22 1988-09-20 Electronic air-fuel ratio control apparatus in internal combustion engine Expired - Lifetime US4915080A (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP62-236300 1987-09-22
JP23630087A JPS6480749A (en) 1987-09-22 1987-09-22 Air-fuel ratio control device for internal combustion engine
JP62238957A JPH0786332B2 (ja) 1987-09-25 1987-09-25 内燃機関の空燃比制御装置
JP62-238957 1987-09-25

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Cited By (22)

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US5251604A (en) * 1990-06-19 1993-10-12 Nissan Motor Company, Ltd. System and method for detecting deterioration of oxygen sensor used in feedback type air-fuel ratio control system of internal combustion engine
US5329764A (en) * 1993-01-11 1994-07-19 Ford Motor Company Air/fuel feedback control system
US5341643A (en) * 1993-04-05 1994-08-30 Ford Motor Company Feedback control system
US5417060A (en) * 1991-05-13 1995-05-23 Nippondenso Co., Ltd. Air fuel ratio control apparatus for an internal combustion engine
US5443711A (en) * 1988-12-02 1995-08-22 Ngk Spark Plug Co., Ltd. Oxygen-sensor element
US5452576A (en) * 1994-08-09 1995-09-26 Ford Motor Company Air/fuel control with on-board emission measurement
US5490490A (en) * 1995-04-27 1996-02-13 Ford Motor Company On-board gas composition sensor for internal combustion engine exhaust gases
US5538612A (en) * 1987-12-09 1996-07-23 Ngk Spark Plug Co., Ltd. Oxygen sensor element
US5705129A (en) * 1995-04-10 1998-01-06 Ngk Insulators, Ltd. NOx sensor
US5849165A (en) * 1988-11-01 1998-12-15 Ngk Spark Plug Co. Ltd. Oxygen sensor for preventing silicon poisoning
US5980710A (en) * 1997-05-21 1999-11-09 Denso Corporation Method and apparatus for gas concentration detection and manufacturing method of the apparatus
US6279537B1 (en) * 1999-06-07 2001-08-28 Mitsubishi Denki Kabushiki Kaisha Air fuel ratio control apparatus for an internal combustion engine
US6446488B1 (en) * 1998-05-29 2002-09-10 Denso Corporation Gas concentration measuring apparatus producing current signals as a function of gas concentration
US6810659B1 (en) * 2000-03-17 2004-11-02 Ford Global Technologies, Llc Method for determining emission control system operability
US6860100B1 (en) 2000-03-17 2005-03-01 Ford Global Technologies, Llc Degradation detection method for an engine having a NOx sensor
US20050133381A1 (en) * 2003-12-17 2005-06-23 Kerns James M. Dual mode oxygen sensor
US20100204904A1 (en) * 2007-10-24 2010-08-12 Toyota Jidosha Kabushiki Kaisha Air-fuel ratio control apparatus and air-fuel ratio control method for internal combustion engine
WO2013049335A3 (fr) * 2011-09-28 2013-05-23 Continental Controls Corporation Système et procédé de réglage automatique de point de consigne pour système de régulation du rapport air-carburant d'un moteur
US8763594B2 (en) 2009-12-04 2014-07-01 Ford Global Technologies, Llc Humidity and fuel alcohol content estimation
US20140220691A1 (en) * 2013-02-01 2014-08-07 Ford Global Technologies, Llc Determination of a degree of aging of an oxidizing catalytic converter
US9518529B2 (en) 2013-10-11 2016-12-13 Ford Global Technologies, Llc Methods and systems for an intake oxygen sensor
US20180283302A1 (en) * 2017-04-04 2018-10-04 Toyota Jidosha Kabushiki Kaisha Exhaust purification system of internal combustion engine

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JPH1068346A (ja) * 1996-06-21 1998-03-10 Ngk Insulators Ltd エンジン排ガス系の制御法
DE19739848A1 (de) * 1997-09-11 1999-03-18 Bosch Gmbh Robert Brennkraftmaschine insbesondere für ein Kraftfahrzeug
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EP2711519A4 (fr) * 2011-05-16 2017-09-27 Toyota Jidosha Kabushiki Kaisha Dispositif de commande de rapport air/carburant pour moteur à combustion interne
KR20210105665A (ko) * 2020-02-19 2021-08-27 현대자동차주식회사 조기 점화시 공연비 제어 방법 및 공연비 제어 시스템

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US5538612A (en) * 1987-12-09 1996-07-23 Ngk Spark Plug Co., Ltd. Oxygen sensor element
US5849165A (en) * 1988-11-01 1998-12-15 Ngk Spark Plug Co. Ltd. Oxygen sensor for preventing silicon poisoning
US5443711A (en) * 1988-12-02 1995-08-22 Ngk Spark Plug Co., Ltd. Oxygen-sensor element
US5251604A (en) * 1990-06-19 1993-10-12 Nissan Motor Company, Ltd. System and method for detecting deterioration of oxygen sensor used in feedback type air-fuel ratio control system of internal combustion engine
US5417060A (en) * 1991-05-13 1995-05-23 Nippondenso Co., Ltd. Air fuel ratio control apparatus for an internal combustion engine
US5329764A (en) * 1993-01-11 1994-07-19 Ford Motor Company Air/fuel feedback control system
US5341643A (en) * 1993-04-05 1994-08-30 Ford Motor Company Feedback control system
US5452576A (en) * 1994-08-09 1995-09-26 Ford Motor Company Air/fuel control with on-board emission measurement
US5705129A (en) * 1995-04-10 1998-01-06 Ngk Insulators, Ltd. NOx sensor
US5490490A (en) * 1995-04-27 1996-02-13 Ford Motor Company On-board gas composition sensor for internal combustion engine exhaust gases
US5980710A (en) * 1997-05-21 1999-11-09 Denso Corporation Method and apparatus for gas concentration detection and manufacturing method of the apparatus
US6226861B1 (en) 1997-05-21 2001-05-08 Denso Corporation Method and apparatus for gas concentration detection and manufacturing method of the apparatus
US6446488B1 (en) * 1998-05-29 2002-09-10 Denso Corporation Gas concentration measuring apparatus producing current signals as a function of gas concentration
US6279537B1 (en) * 1999-06-07 2001-08-28 Mitsubishi Denki Kabushiki Kaisha Air fuel ratio control apparatus for an internal combustion engine
US7059112B2 (en) 2000-03-17 2006-06-13 Ford Global Technologies, Llc Degradation detection method for an engine having a NOx sensor
US6810659B1 (en) * 2000-03-17 2004-11-02 Ford Global Technologies, Llc Method for determining emission control system operability
US6860100B1 (en) 2000-03-17 2005-03-01 Ford Global Technologies, Llc Degradation detection method for an engine having a NOx sensor
US6990799B2 (en) 2000-03-17 2006-01-31 Ford Global Technologies, Llc Method of determining emission control system operability
US20050133381A1 (en) * 2003-12-17 2005-06-23 Kerns James M. Dual mode oxygen sensor
US7449092B2 (en) * 2003-12-17 2008-11-11 Ford Global Technologies, Llc Dual mode oxygen sensor
US20090090339A1 (en) * 2003-12-17 2009-04-09 Ford Global Technologies, Llc Dual Mode Oxygen Sensor
US8354016B2 (en) 2003-12-17 2013-01-15 Ford Global Technologies, Llc Dual mode oxygen sensor
US20100204904A1 (en) * 2007-10-24 2010-08-12 Toyota Jidosha Kabushiki Kaisha Air-fuel ratio control apparatus and air-fuel ratio control method for internal combustion engine
US8249793B2 (en) * 2007-10-24 2012-08-21 Toyota Jidosha Kabushiki Kaisha Air-fuel ratio control apparatus and air-fuel ratio control method for internal combustion engine
US8763594B2 (en) 2009-12-04 2014-07-01 Ford Global Technologies, Llc Humidity and fuel alcohol content estimation
US8887706B2 (en) 2009-12-04 2014-11-18 Ford Global Technologies, Llc Humidity and fuel alcohol content estimation
WO2013049335A3 (fr) * 2011-09-28 2013-05-23 Continental Controls Corporation Système et procédé de réglage automatique de point de consigne pour système de régulation du rapport air-carburant d'un moteur
US9303575B2 (en) 2011-09-28 2016-04-05 Continental Controls Corporation Automatic set point adjustment system and method for engine air-fuel ratio control system
US20140220691A1 (en) * 2013-02-01 2014-08-07 Ford Global Technologies, Llc Determination of a degree of aging of an oxidizing catalytic converter
US9784721B2 (en) * 2013-02-01 2017-10-10 Ford Global Technologies, Llc Determination of a degree of aging of an oxidizing catalytic converter
US9518529B2 (en) 2013-10-11 2016-12-13 Ford Global Technologies, Llc Methods and systems for an intake oxygen sensor
US20180283302A1 (en) * 2017-04-04 2018-10-04 Toyota Jidosha Kabushiki Kaisha Exhaust purification system of internal combustion engine

Also Published As

Publication number Publication date
EP0308870B1 (fr) 1992-05-06
EP0308870A2 (fr) 1989-03-29
EP0308870A3 (en) 1989-10-25
DE3870782D1 (de) 1992-06-11

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